1. Field of the Invention
This invention relates to a fuse housing for a network protector and, more specifically, to a fuse housing that is constructed using a reduced number of parts.
2. Description of the Prior Art
Secondary power distribution networks consist of interlaced grids which are supplied by two or more sources of power so that the loss of a single source of power will not result in an interruption of service. Such networks provide the highest level of reliability possible with conventional power distribution and are normally used to supply high-density load areas such as a section of a city, a large building, or an industrial site. Between the power sources and the network is a transformer and a network protector. Such network protectors are often found in dust-proof or moisture-proof housings which are disposed in subterranean passageways in large metropolitan areas. The housing, or xe2x80x9ctank,xe2x80x9d may be further disposed within a concrete vault.
The network protector consists of a circuit breaker and a control relay. The control relay senses the transformer and network voltages and line currents and executes algorithms to initiate breaker tripping or closing action. The network protector is, typically, coupled to the line and the load by a three phase bus. Network protectors often utilize fuses as a secondary means of protection. Thus, there are fuses installed on each of the phases. Because interruption of a fuse inside the network protector housing often results in damage to the circuit breaker or other components, it is often preferable to have the fuses located outside of the network protector housing.
The fuses are enclosed in separate watertight housings disposed on top of the network protector housing. The prior art fuse housings are made from steel or molded fiber reinforced epoxy resin. The molded fuse housings are expensive. The steel fuse housings are less expensive, but are prone to leaks around the welded joints. Moreover, because each fuse has a separate housing, there are multiple welded joints that have the potential to leak. When water penetrates the fuse housing, the fuse may be damaged or degraded, thus limiting the ability of the fuse to interrupt the circuit.
There is, therefore, a need for an inexpensive fuse housing that is less prone to leakage.
There is a further need for a new fuse housing that is compatible with existing network protectors.
These needs, and others, are satisfied by the invention which provides a network protector fuse housing that is constructed using a two clam shell halves and which is structured to enclose all fuses connected to the network protector. The clam shell halves are constructed of stamped steel and have elongated U-shaped bodies. The U-shaped bodies are welded together to form the housing. Thus, there are eight welded joints on the housing. The number of welded joints is reduced relative to the prior art fuse housings which had at least eight welded joints on each of three individual housings.
The fuse housing may be mounted on the tank or, if space within the vault is an issue, on a wall adjacent to the network protector. The fuse housing may also have access portals located adjacent to each fuse, or, one large portal providing access to every fuse within the housing. The portal(s) is sealed with a cover that is coupled to the housing by fasteners.